1. The Field of the Invention
The present invention relates to methods and apparatus for supporting or immobilizing a body part. More specifically, the present invention relates to methods and apparatus for making and using a custom-fit, lightweight, durable orthopedic appliance (or xe2x80x9corthopedic splintxe2x80x9d) for use as a splint, cast, or protective pad.
2. The Relevant Technology
Many common injuries require that a body part or surface be covered with a protective dressing in order to provide support, promote healing, prevent further injury, selectively immobilize the injury, and act as a shock-absorbent buffer around it. In many such injuries, especially where the hard, durable dressings currently known in the art are used, it is generally preferred that the dressing be kept in place once it has been applied. This may be desired in order to preserve the precise setting of a bone needed for proper healing, to prevent the patient from moving or using the injured part, to enclose and protect an open wound, or to accomplish a combination of these functions.
Durable, long-lasting dressings such as these are key to medical efficiency and treatment since they can last weeks without replacement by a doctor. This saves both the patient and the doctor significant time, expense, and discomfort. Dressings of this type are often required after accidental injuries, and may also be used after some surgical procedures.
Methods and devices for stabilizing body parts and surfaces face challenges to be successful. First, since a dressing may need to be worn for extended periods, it is preferably clean; strong; resistant to wear, degradation, and rotting, etc.; waterproof, and presentable in appearance. This helps such dressings to remain clean and sterile and to protect the underlying skin from irritation and infection.
Since many emergency situations require the immobilization of a body part or surface, dressings which are quick to apply and which are strong and supportive are preferred. Further, in such emergency or first aid situations, such dressings should be easy to apply and use, thus allowing them to be employed by untrained volunteers when no trained medical personnel are available.
Finally, in an era when people are embracing lifestyles of increased physical activity, patients demand that casts and splints leave them able to participate in as many activities as possible. As a result, lightweight, small, waterproof, and strong solutions to the casting problem are advantageous.
Many methods and devices are currently known and relied on in the art for stabilizing body parts or surfaces. Prime examples of these are casts and splints including plaster casts, casts made up of synthetic resins, and splints made of resins, plastics, or metals. Many of these materials are easily conformable to the shape and size of the body part of the patient, and are able to strongly support the needed limb.
Plaster casts were formerly the most widely used form of casting. In this casting method, strips of cloth impregnated with plaster are immersed in water and carefully wound around the affected limb in layers. This mass is then painstakingly shaped and then allowed to harden over a period which may last hours to obtain a full set of the plaster. The result is a thick, solid, and often heavy cast amply capable of supporting the injured limb.
Such plaster casts are useful in many applications, but also generally suffer from disadvantages ranging from long setting periods during which the cast is not solid, and which may thus be more easily damaged, high weight and density, impermeability to X-rays, susceptibility to damage and weakening from exposure to water, and bulkiness.
Casts made of synthetic resins have become popular in recent years due to their ability to harden in a shorter period of time (relative to plaster), their lighter weight and lower density (relative to plaster), their resistance to damage from water, their permeability to X-rays, and the ability to provide them in attractive colors. These casts are popular among wearers since they are lighter and less bulky, while still retaining the needed characteristic of strength. The drawbacks of this technology include the need for wet handling and clean up or special equipment, including in some cases, equipment for producing UV rays to harden the resins, and lesser ability to form and mold the casting material.
In addition to these techniques, there is a wide range of technologies available for removably splinting a wound. These technologies allow the patient to remove the dressing when needed and replace it on their own. Many such devices involve metal or plastic supports which are pre-formed and molded within padding or foam to brace the wound. Though useful in many applications, these devices are only very poorly adaptable to the anatomy of the user, and involve increased cost, weight, and inconvenience.
Accordingly, a need exists for a lightweight orthopedic splint appliance useful for casting and splinting wounds which is easy to use, moldable to the anatomy of the patient, quick to harden without water application or external chemicals, strong, durable, waterproof, and attractive. It would be an advancement in the art to provide a self-contained orthopedic splint that does not require the use of water, gloves, or other accessories to enable use in the field or any other circumstance. Such a device is disclosed herein.
The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available orthopedic splint and casting systems, including those referenced above.
To achieve the foregoing objects, and in accordance with the invention as embodied and broadly described herein, a form-in-place orthopedic splint system is provided. The orthopedic system includes an outer envelope having an inner face and an outer face, where the inner face has a textured surface. The outer envelope contains a liquid polyol composition which is in contact with this textured surface of the inner face. The inner envelope contains an isocyanate composition, and keeps the isocyanate segregated from the polyol in the interior of the outer envelope. This inner envelope is adapted, however, to be ruptured by a user, thus allowing the polyol and isocyanate to mix and react, causing the formation of a polyurethane foam. The inner envelope may be ruptured by many means currently known in the art including, but not limited to, pressure, tension, physical perforation, tearing, and puncturing. In many forms of the instant invention, the inner and outer envelopes may be made of a high density polyethylene or similar polymeric material. Polyethylene is notably suitable since it is an oriented plastic which may be easily torn in a predictable direction. Polyethylene is substantially water impermeable, and thus prevents water from entering the envelopes containing the reagents. The materials used in the envelopes should be substantially water impermeable to prevent the entry of water into the envelopes since water will react with isocyanate, thus fouling the reaction with the polyol composition. In some forms, the inner envelope is between about 2 and about 4 mils thick. In others, the high density polyethylene is about 2 mils thick.
In many of these embodiments of the instant invention, the outer envelope of the orthopedic splint is shaped and configured to conform to a specific body part. Specifically, the orthopedic splint may be adapted to conform to the hand, elbow, wrist, thumb, forearm, shoulder, foot, ankle, knee, leg, or other desired body parts. Those skilled in the art of constructing orthopedic splints and casts would be familiar with such known useful splint shapes, styles, and conformations.
The polyurethane foam may be adapted to have a relatively short cure time of between about 8 and 15 minutes. In some forms of the instant invention, the polyol and isocyanate are selected to yield a curing time of less than about 12 minutes. In a presently-preferred embodiment, the polyol and isocyanate reagents are selected to yield a curing time of about 10 minutes. This amount of time is sufficient to allow a medical professional to mold the cast to fit the shape of the body part or surface to be supported, while still reducing the amount of time that the patient has to remain motionless and that the doctor has to spend monitoring the patient. The exact amount of time needed for the polyurethane foam to cure is dependent upon the polyol and isocyanate chosen, and may thus be modified or adjusted to meet a chosen cure time.
In preferred embodiments of the invention, the reagents are chosen to yield a mix/cream time of about 2 minutes. During this time, the isocyanate and polyol may be easily kneaded together and mixed. After this, a rise time of approximately 4 minutes ensues in which the polyurethane foam rises and may begin to be molded to conform to the body part or surface to be supported, splinted, or cast. Following this period, a demold period of about four minutes ensues in which the polyurethane may still be shaped, though with more effort, and after which (at about 10 minutes from disrupting the inner envelope), the polyurethane is firm enough to provide adequate support to the body part. The reagents may also comprise coloring agents to give a color to the orthopedic splint.
The thickness of the orthopedic splint system is also carefully monitored so as to promote even strength and distribution of the foam while protecting the patient against exposure to uncomfortable or dangerous amounts of heat produced by the exothermic reaction involved in the formation of the polyurethane foam.
The polyurethane foam generated within the orthopedic splint upon mixing the polyol and isocyanate preferably has a density of between about 8 and about 12 pounds per cubic foot. In a presently-preferred embodiment of the invention, the polyurethane foam has a density of about 10 pounds per cubic foot.
The foam is adapted to harden to a useful stiffness and to adhere to the textured surface of the inner face of the inner envelope. The novel texturing of the plastic inner face dramatically increases the surface area of the inner face available to the foam for bonding, and also mechanically increases the strength of the bond formed at the interface of the foam and the envelope. A vast variety of textures may be used within the scope of the instant invention, with those being favored which maximize the surface area of the inner face. The textures are also constrained by the thickness of the outer envelope, which is preferably comprised of a high density polyethylene of between about 2 and about 4 mils in thickness. Though polyethylene is preferred for the inner and outer envelopes, materials such as Mylar, polypropylene, and others with similar properties, may be used. In addition, though the foam of the invention is preferably polyurethane, as described above, other polymeric foams which are appropriate for use with the invention may be used. The inner envelope may also be textured on its outside, or on all of its faces, and is generally comprised of a high density polyethylene of about 2 to about 4 mils in thickness.
Additionally, in some forms of the instant invention, the inner envelope is securely disposed at a fixed location within the outer envelope. In some of these, the inner envelope is secured to a corner of the outer envelope by one edge, and in others, by two edges. In others, the inside face of the outer envelope comprises part of the inner envelope. This predictability of location of the inner envelope makes the orthopedic splint system of the instant invention easy to use since the location of the needed reagent is fixed, and it may be quickly isolated and ruptured by the user.
Further, since the inner envelopes are known to often produce a structurally weakened region in the final hardened product, it is an improvement in the art to control the location of the possible weakened region so as to allow that region of the system to be placed in a region of minimum strength requirements. Indeed, in some forms of the invention where the outer envelope is shaped and adapted to conform to a specific body part, the inner envelope may be located at a position which does not interfere with the usefulness or strength of the resulting orthopedic splint device during the construction of the device. Further, the inner envelope may be comprised of a high-density polyethylene of between 2 and 4 mils in thickness. It may, as noted above, be textured on any or all faces to increase the strength of the bond of the polyurethane foam material with the envelope.
The xe2x80x9cinner envelopexe2x80x9d may also be placed outside of the outer envelope with a channel connecting its interior to the interior of the outer envelope. The channel may have a seal to isolate the foam producing reagents prior to activation. This seal may be frangible such that an application of pressure to the inner envelope will cause the seal to rupture, thus opening the channel into the outer envelope. The inner envelope may additionally be removable from the splint after use. This may be accomplished by using a frangible seam to connect the inner envelope to the outer envelope, as well as simply making it possible to sever the inner envelope with a sharp instrument.
In other forms, the instant invention comprises a method of stabilizing a body part or surface. A first step is obtaining an orthopedic splint of the instant invention as described above. This orthopedic splint will comprise an outer envelope having an inner face with a textured surface and an outer face which could also be textured. The outer envelope contains a polyol which is in contact with said textured surface of said inner face; and the inner envelope contains an isocyanate composition. The inner envelope is adapted to be ruptured by a user, thus allowing the polyol and composition to be mixed. A second step is the rupturing of the inner envelope and the subsequent mixing of the polyol and the isocyanate catalyst to cause the formation of a polyurethane foam. A next step is molding the orthopedic splint device to conform to the anatomical shape of the body part or surface to be supported. A following step is allowing the polyurethane foam to harden to a useful stiffness and adhere to the textured surface of the inner face within a predetermined curing time. Factors such as the predetermined curing time, the density of the foam, and the anatomical shape and characteristics of the device itself may be varied as taught herein within the scope of this method.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.